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I'm studying basic electronics from the sound reinforcement handbook and I think I see an error in the book, so i'm kind of worried i might not learn the material right. I need to to find out about current flow and its direction. So:

If I put a 9v battery on my tongue, does the current flow from positive > tongue > negative or does it flow from negative > tongue > positive?

The book says it would flow from negative, but I watched a video from a university class on electricity (you tube) that said that electricity flows from the positive.

Thats my pickle.

Comments

taxman Tue, 03/18/2008 - 09:48

This is an area of continued confusion, of no fault of your own.

"Conventional" diagrams show current flow from the positive to the negative terminal. The reason is entirely historical, because that what seemed appropriate. It was only after significantly more was learned about what was happening at the subatomic level that physicists and engineers determined that the electrons, which are negatively charged are migrating, ie flowing.

Some college textbooks on electronic therory are published in two versions of the text, with one showing conventional and and the other version showing actual current flow.

BobRogers Tue, 03/18/2008 - 10:02

On a historical note, the convention of the sign of charge is due to Ben Franklin. His one-fluid model of electricity is arguably the first important contribution to science by an American. Now that we understand things better at a subatomic level it is common to refer to current as the flow of "holes" where electrons are absent.

If you are mathematically inclined, you can remember the convention that the electric field is negative the gradient of the voltage (so it points from positive to negative voltage), and the current is proportional to the electric field.

So yeah, it's not common sense at all. Requires memorization of arbitrary conventions.

Boswell Tue, 03/18/2008 - 11:23

In the standard definition, current flows from a positive terminal to a negative terminal. In an ordinary conductor, this current flow actually is made up of negatively charged electrons flowing the other way.

Voltage does not come into it, other than being the driving force behind the current flow.